How can I enforce my visitation if mom won’t allow it?

I have been divorced for 10 years and I've had shared custody of my twin daughters who are now 14 years old. I met a woman 3 1/2 years ago and she as well as twin daughters now 17 years old. For the first two years of our relationship, my daughters and my new wife's daughters were best friends. They were inseparable. My daughters and their new stepmom are also very close. They shopped, cooked and did other activities together. We all went on vacations together cruises, Disney, camping. Two years into my relationship, I spoke to my children and asked them how they would feel if I was to get remarried. They were very happy and excited. Two days after I spoke to my children, my ex-wife confessed that she still love me and no one could ever love me the way she does. She has also been remarried for about eight years now. Within days after our conversation, my children will no longer come and visit me anymore. They said that they hate my new wife and has never liked her. They were acting. My children has made accusations against my wife stating she beats her own children all the time as well as curses at them all the time. When they came to the house for visitations, they were made to feel like they had to steal food because it was not provided with him. All of which is not true. For the last year and a half, my children have refused to come to my home to refuse visitations on weekends. I will only see them if I am not near my wife or my now stepchildren. They stated that they are afraid to come to the house because my wife will mentally and emotionally hurt them. I've never enforced my weekend visitations as I do not want to force them to do something they do not want but I am at the point I want to spend more time with my children. When I pick my children up on midweek visitations from school for last year, I've been taking them to parks or restaurants because they refuse to be around my wife. This is causing a huge separation between myself and my wife and it needs to stop.